Metadata is often described as “data about data.” Metadata can take various forms, which range from simple to complex. In one simple example, a computer file is associated with metadata, which may include the name and type of the file, the creation and last-modified dates, the access permissions, etc. In a more complex example, data follows a complex, multi-layered structure, in which case the metadata may include a schema that defines the structure of the data.
One way to view metadata is that it is merely one kind of data. However, in practice, the management of metadata presents issues that are somewhat different from management of the underlying data to which the metadata relates. The metadata may be accessed more frequently than the underlying data. Moreover, an access failure for metadata may be considered less acceptable than an access failure for ordinary data.